A stepping motor has been conventionally used as a motor in an optical pickup device which is used in a CD player and a DVD player or as a motor for moving a lens group used in a camera. As this type of a stepping motor, a stepping motor which is provided with pole teeth fixed to an outer yoke and pole teeth fixed to an inner yoke has been known (see, for example, Patent Literature 1).
In the stepping motor described in Patent Literature 1, the pole teeth fixed to the outer yoke and the pole teeth fixed to the inner yoke are alternately disposed in a circumferential direction of the rotor and the pole teeth are disposed so as to face an outer peripheral face of a drive magnet structuring the rotor. Further, in the stepping motor, the pole teeth are formed in a substantially trapezoid shape and spaces in the circumferential direction between the pole teeth fixed to the outer yoke and the pole teeth fixed to the inner yoke are set to be constant in an axial direction of the rotor.
Patent Literature    [PTL 1] Japanese Patent Laid-Open No. 2000-50536
In markets such as a CD player and a DVD player or a camera, the size of the device has been required to reduce in recent years and thus the size in the axial direction of a stepping motor mounted on the device is also required to reduce. On the other hand, even when the size in the axial direction of the stepping motor is reduced, the performance of the stepping motor is required in the market to be similar to that of the motor before downsizing.
In view of the problem described above, at least an embodiment of the present invention is to provide a stepping motor in which deterioration of its performance is restrained even when the size in the axial direction is reduced.